1. Field of the Invention
The present invention relates to a method of operating IPv4-network-compatible applications on an IPv6network, a packet generation method, an IP-network-dedicated translator and an NAT (Network Address Translator) as well as a recording medium having a packet generation program recorded thereon.
2. Description of Related Art
Among the protocols for the network layers employed in the TCP (Transmission Control Protocol)/IP (Internet Protocol) communications, the: one most familiar in the present state of the art is the IP. At present, the IP of version 4 (hereinafter referred to as the IPv4) is prevailing. Although the IP is currently winning popularity more and more at a high rate in various communication service fields, keeping step with spreading of the internet, the IP nevertheless confronts a serious problem in respect to the exhaustion of IP address.
As measures for solving the above problem, there are proposed currently such a provisional solution that private address space of the IPv4 is locally provided for local LANs (Local Area Networks) as well as an IP of version 6 (hereinafter referred to as the, IPv6). In the present state of the art, a large scale LAN is being realized in which there coexist mixedly the LANs conforming to the IPv6 and the LANs conforming to the IPv4, respectively. As a document concerning the standards for the interconnection of the IPv6-based LAN and the IPv4-based LAN, there can be mentioned xe2x80x9cRFC1933xe2x80x9d. According to the RFC1933 (Transition Mechanism for IPv6 and Routers; R. Gilligan, 1996, April, IETF), interconnection of the IPv6 network is rendered possible by mapping the IPv4 address to the IPv6 address.
As mentioned above, although the IPv6 network is on the way of being developed, the number of the APs (Application Programs) conforming to or compatible with the IPv6 is very small as compared with the, IPv4-compatible APs. It is further noted that there has not yet been available such means which allows the IPv4-compatible application operating on a PC (Personal Computer)/WS (Work Station) and the IPv6-compatible application on a PC/WS to communicate directly with each other without resorting to the aid of a network having an NAT function such as the address translation router or the like. In the case where the address translation router is employed, protocol conversion is performed in addition to, the routing processing known heretofore. Thus, a heavy load is imposed on the address translation router. By the way, the IPv4 packet dedicated to the hardware address resolution undergoes no conversion. In order that an existing IPv4-compatible AP can perform communication without consciousness of the IP address of a connection-destined host, a logical-name-based address resolution relying on a DNS (Domain Name System) is indispensably required.
With the present invention, it is contemplated as an object thereof to make it possible that an IPv4 -compatible APs operating on a PC/WS can communicate directly with an IPv6-compatible application on a host such as a PC/WS or the like without need for intervention of network equipment such as the address translation router or the like imparted with the NAT function.
Another object of the present invention is to provide a DNS function conforming to or compatible with the IPv6 (IPv6 address inquiry function) in order to make it possible for an IPv4-compatible AP to perform communication without consciousness of the address of a communication counterpart.
Yet another object of the present invention is to make it possible that a packet for hardware address resolution conforming to or compatible with the IPv4 as issued by an existing AP can be converted to a hardware-address-resolution-dedicated packet conforming to or compatible with the IPv6 with a view to enabling an IPv4-compatible AP to communicate with an IPv6-compatible AP.
The information processing apparatus such as PC/WS or the like which is imparted with a LAN control function (hereinafter also referred to as the LAN control apparatus) and to which the present invention can find application includes ordinarily IPv4-compatible APs and an IPv4 protocol control module. Ordinarily, the above-mentioned LAN control function is realized mainly through a program, so-called software, and there is additionally provided hardware destined for performing transmission/reception controls for the communication media.
For achieving the objects mentioned above, a protocol conversion control module is provided between an IPv4 protocol control module and a LAN control module both for the LAN control function. The protocol conversion control module includes an IPv4-IPv6 switch control module, a buffer conversion module, a header conversion control module, an IPv6 transmission/reception control module and a DNS-NAT cooperation or cooperation control module. The protocol conversion control module converts the IPv4 packet outputted from the IPv4 protocol control module to the IPv6 packet and outputs the latter to the LAN control module. Further, the IPv6 packet outputted from the LAN control module is converted to the IPv4 packet to be subsequently outputted to the IPv4 protocol control module.
Controls and data flows among the individual control modules are as follows.
In the case of transmission, data is transferred from an IPv4-compatible AP to the IPv4 protocol control module, while the IPv4 protocol conversion control module transfers the IPv4 packet to the protocol conversion control module. The protocol conversion control module interprets the packet as transferred, to thereby perform processings described below. In the case of an ARP request packet, the protocol conversion control module messages a hardware address as generated to the IPv4 protocol control module. In that case, the actual hardware address resolution is realized by performing address resolution with the IPv6 protocol.
In the case of inquiry packet of the DNS, the protocol conversion control module inquires both the IPv6 address and the IPv4 address, and when the IPv6 address is returned as a response packet, the IPv4 address which corresponds to the IPv6 address is transmitted to the IPv4 protocol control module.
In the case of an ordinary packet, the protocol conversion control module checks the IPv4 address of a send destination as contained in the IPv4 header to thereby perform processings mentioned below. When the above address is one registered in an address translation table incorporated in the protocol conversion control module, the protocol conversion control module translates the address of concern to the IPv6 address on the basis of the address translation table to thereby generate an IPv6 header, which is then sent onto the LAN in the form of IPv6 packet. Unless the address of concern is registered in the address translation table incorporated in the protocol conversion control module, the protocol conversion control module sends the IPv4 packet intactly onto the LAN.
In the case of reception, when an IPv6 packet is received from the LAN control module, the protocol conversion control module checks the IPv6 address of the source sender as contained in the IPv6 header. When the address mentioned above is one registered in the address translation table incorporated in the protocol conversion control module, the protocol conversion control module translates that address to the corresponding IPv4 address to thereby generate an IPv4 header and transfer the IPv4 packet data to the IPv4 protocol control module of higher level.
In the case where the IPv6 address is not registered in the address translation table incorporated in the protocol conversion control module, the protocol conversion control module discards the received packet. Upon reception of the IPv4 packet from the LAN control module, the protocol conversion control module transfers the data of the other packet than the DNS response packet to the protocol control module. In this manner, it is possible to make the IPv4-compatible AP communicate with the IPv6-compatible AP.
By adopting the means described above, the objects mentioned previously can be achieved.
Thus, by providing the protocol conversion control module between the protocol control module and the LAN control module known heretofore so that the protocol conversion control module performs header conversion between the IPv4 header and the IPv6 header for the packets flowing between the protocol control module and the LAN control module, the application program which transfers data to the protocol control module can carry out the communication with other apparatus connected to the IPv6 network in accordance with the IPv6, even when the former is the IPv4-compatible application.